1. Technical Field of the Invention
This invention relates to radio telecommunication systems and, more particularly, to a method of controlling paging in a plurality of mobile switching centers (MSCs) in a radio telecommunications network.
2. Description of Related Art
In existing radio telecommunications networks, there are currently both analog and digital mobile stations in operation. Estimates of the number of analog mobile stations in operation indicate that there may be approximately 70 million analog mobile stations in operation despite the introduction of digital mobile stations a number of years ago. Therefore, cellular telecommunications networks must continue to support analog mobile stations for years to come, and solutions to problems that are unique to analog mobile stations are still desirable.
A common problem with analog mobile stations is their tendency to rescan for control channels prior to making a network access over the air interface. This tendency to rescan results in various border-related problems when the mobile stations are located near a border mobile switching center (border MSC). For example, several page attempts may be required in both a serving MSC and border MSCs to locate a mobile station operating near the border. Some of these problems were solved at the network level through the introduction of the InterSystemPage and the UnsolicitedPageResponse messages. However, when multiple page attempts are required, multiple intersystem signaling messages must be sent, adding considerably to the intersystem signaling load.
In existing telecommunications networks, the serving MSC sends an InterSystemPage message to the border MSCs associated with the paging area. When the page response time in the serving MSC expires and no page response has been received from either the serving MSC or a border MSC, another paging attempt may be performed, if defined by the operator. If the next paging attempt also covers a paging area spanning multiple MSCs, another InterSystemPage message must be sent from the serving MSC to the border MSCs. This is a burdensome amount of signaling. In addition, the serving MSC does not know whether any of the border MSCs are still in the process of paging for the mobile station, or if an unreported fault has occurred. Also, call disconnections may occur due to system timeout and the fact that there may be insufficient time following a no page response to transfer the call to voice mail.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that described and claimed herein.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a method of controlling paging in a plurality of mobile switching centers in a radio telecommunications network. Such a method would increase the probability of delivering a call to an analog mobile station located close to an intersystem border, deliver the call while minimizing the signaling load between the cross-border MSCs, decrease the call setup time, and reduce the number of call disconnections due to system timeout by ensuring that the home location register (HLR) of the called party has sufficient time to allow the call to be transferred to voice mail in the event there is no page response from the called mobile station. The present invention provides such a method.